Degradation of iopamidol in the permanganate/sulfite process:Evolution of iodine species and effect on the subsequent formation of disinfection by-products

Permanganate/sulfite(Mn(VII)/S(IV))process is a promising pre-oxidation technology for sequestering the emerging organic contaminants in drinking water treatment plant.Iopamidol(IPM),a representative of iodinated X-ray contrast media,has been widely detected in water sources and has the risk of forming iodinated disinfection byproducts(I-DBPs)in water treatment system.In this study,we investigated the evolution of iodine species during the IPM degradation by the Mn(VII)/S(IV)process and its effect on the subsequent formation of I-DBPs during chlorination at pH 7.0 and 8.0.IPM could be effectively degraded in the Mn(VII)/S(IV)process at environmentally relevant pH(pH 7.0 and 8.0).The results of quenching and competitive oxidation kinetic experiments revealed that SO^(·-)_(4)was the major reactive oxidizing species contributing to the degradation of IPM whereas the contributions of HO·and reactive manganese species were negligible in the Mn(VII)/S(IV)process.I–and IO–3were generated while no HOI was detected during the degradation of IPM in the Mn(VII)/S(IV)process.The effects of IPM oxidation by Mn(VII)/S(IV)on the subsequent formation of chlorinated disinfection by-products(Cl-DBPs)during chlorination were related to the category of Cl-DBPs.The pre-oxidation of IPM by Mn(VII)/S(IV)resulted in the generation of I-DBPs during the disinfection process although no I-DBPs were detected if no pre-oxidation was applied.The finding of this study suggested that attention should be paid to the toxicity of DBPs when water containing iodinated organic contaminants is treated by Mn(VII)/S(IV)process or other pre-oxidation technologies.

基于高铁酸盐的水污染控制技术研究进展

高铁酸盐(FeO4^2-, Fe(Ⅵ))是一种同时具有氧化、吸附、絮凝、杀菌、消毒等多种功能的绿色水处理剂,因独特的环境友好特性而受到人们越来越多的关注.本文主要介绍了Fe(Ⅵ)的氧化特性及机理,综述了近年来基于Fe(Ⅵ)的水处理技术研究进展,包括Fe(Ⅵ)氧化新兴有机污染物及强化方面的研究、Fe(Ⅵ)杀菌消毒作用及其氧化过程中消毒副产物生成情况、Fe(Ⅵ)氧化和自分解产生的新生态铁氧化物的特性及其去除重(类)金属的机理,并对未来的研究方向和发展趋势进行了展望.

Preparation and application of amino functionalized mesoporous nanofiber membrane via electrospinning for adsorption of Cr^(3+) from aqueous solution

Novel amino （-NH2） functionalized mesoporous polyvinyl pyrrolidone （PVP）/SiO2 composite nanofiber membranes were fabricated by a one-step electrospinning method using poly （vinyl alcohol） and tetraethyl orthosilicate （TEOS） mixed with cationic surfactant, cety｜trimethyl ammonium bromide （CTAB） as the structure directing agent. Ureidopropyltriethoxysilane was used for functionalization of the internal pore surfaces. The membranes were characterized by scanning electron microscopy （SEM）, high-resolution transmission electron microscopy （HRTEM） images, X-ray diffraction （XRD）, Fourier-transform infrared spectroscopy （FT-IR）, element analyzer and Nz adsorption-desorption isotherms, The nanofiber diameters, average pore diameters and surface areas were 100-700 nm, 2.86 nm and 873,62 m2/g, respectively. These mesoporous membranes functionalized with -NH2 groups exhibited very high adsorptions properties based on the adsorption of Cr3＋ from an aqueous solution. Equilibrium adsorption was achieved after approximately 20 rain and more than 97% of chronium ions in the solution were removed. The membrane could be regenerated through acidification.

Application of Fe(Ⅵ)in abating contaminants in water:State of art and knowledge gaps

The past two decades have witnessed the rapid development and wide application of Fe(Ⅵ)in the field of water de-contamination because of its environmentally benign character.Fe(Ⅵ)has been mainly applied as a highly efficient oxidant/disinfectant for the selective elimination of contaminants.The in situ generated iron(III)(hydr)oxides with the function of adsorption/coagulation can further increase the removal of contaminants by Fe(Ⅵ)in some cases.Because of the limitations of Fe(Ⅵ)per se,various modified methods have been developed to improve the performance of Fe(Ⅵ)oxidation technology.Based on the published literature,this paper summarized the current views on the intrinsic properties of Fe(Ⅵ)with the emphasis on the self-decay mechanism of Fe(Ⅵ).The applications of Fe(Ⅵ)as a sole oxidant for decomposing organic contaminants rich in electron-donating moieties,as a bi-functional reagent(both oxidant and coagulant)for eliminating some special contaminants,and as a disinfectant for inactivating microorganisms were systematically summarized.Moreover,the difficulties in synthesizing and preserving Fe(Ⅵ),which limits the large-scale application of Fe(Ⅵ),and the potential formation of toxic byproducts during Fe(Ⅵ)application were presented.This paper also systematically reviewed the important nodes in developing methods to improve the performance of Fe(Ⅵ)as oxidant or disinfectant in the past two decades,and proposed the future research needs for the development of Fe(Ⅵ)technologies.

Remediation of arsenic contaminated soil by sulfidated zero-valent iron

In this study,the influences of sulfidation on zero-valent iron(ZVI)performance toward As(Ⅴ)immobilization in soil were systemically investigated.It was found that,compared to unamended ZVI,sulfidated ZVI(S-ZVI)is more favorable to immobilize As(Ⅴ)in soil and promote the conversion of water soluble As to less mobile Fe-Mn bound As.Specifically,under the optimal S/Fe molar ratio of 0.05,almost all of the leached As could be sequestrated by>0.5 wt.%S-ZVI within 3 h.Although the presence of HA could decrease the desorption of As from soil,HA inhibited the reactivity of S-ZVI to a greater extent.Column experiments further proved the feasibility of applying S-ZVI on soil As(Ⅴ)immobilization.More importantly,to achieve a good As retention performance,S-ZVI should be fully mixed with soil or located on the downstream side of As migration.The test simulating the flooding conditions in rice culture revealed there was also a good long-term stability of soil As(Ⅴ)after S-ZVI remediation,where only 0.7%of As was desorbed after 30 days of incubation.Magnetic separation was employed to separate the immobilized As(Ⅴ)from soil after S-ZVI amendment,where the separation efficiency was found to be dependent of the iron dosage,liquid to soil ratio,and reaction time.Toxicity characteristic leaching procedure(TCLP)tests revealed that the leachability of As from soil was significantly reduced after the S-ZVI amendment and magnetic separation treatment.All these findings provided some insights into the remediation of As(Ⅴ)-polluted soil by ZVI.

Pre-oxidation with KMnO4 changes extra-cellular organic matter's secretion characteristics to improve algal removal by coagulation with a low dosage of polyaluminium chloride

Microcystis aeruginosa was used to study the effect of KMnO4 pre-oxidation on algal removal through coagulation with polyaluminium chloride （PAC）.KMnO4 pre-oxidation improved the coagulation efficiency of algal at a low dosage of PAC.The optimal KMnO4 feeding period was in the stationary growth phase of Microcystis aeruginosa.KMnO4 traumatized the algal cells and stimulated cellular release of organic matter,contributing to the pool of extra-cellular organic matter （EOM）.KMnO4 also decomposed EOM,especially small molecular weight EOM.Lower concentrations of KMnO4,such as 2 mg/L,induced algae cells to produce moderate amounts of new EOM with molecular weights of 11,280,and 1500 kDa.These relatively large molecules combined easily with PAC,promoting coagulation and removal of algae.High concentrations of KMnO4 lysed algae cells and produced much high-molecular-weight EOM that did not enhance flocculation by PAC at lower dosages.

Weak magnetic field accelerates chromate removal by zero-valent iron

Weak magnetic field（WMF） was employed to improve the removal of Cr（VI） by zero-valent iron（ZVI） for the first time. The removal rate of Cr（VI） was elevated by a factor of 1.12-5.89 due to the application of a WMF, and the WMF-induced improvement was more remarkable at higher Cr（VI） concentration and higher p H. Fe2＋was not detected until Cr（VI） was exhausted, and there was a positive correlation between the WMF-induced promotion factor of Cr（VI） removal rate and that of Fe2＋release rate in the absence of Cr（VI） at pH 4.0-5.5. These phenomena imply that ZVI corrosion with Fe2＋release was the limiting step in the process of Cr（VI） removal. The superimposed WMF had negligible influence on the apparent activation energy of Cr（VI） removal by ZVI, indicating that WMF accelerated Cr（VI）removal by ZVI but did not change the mechanism. The passive layer formed with WMF was much more porous than without WMF, thereby facilitating mass transport. Therefore,WMF could accelerate ZVI corrosion and alleviate the detrimental effects of the passive layer, resulting in more rapid removal of Cr（VI） by ZVI. Exploiting the magnetic memory of ZVI, a two-stage process consisting of a small reactor with WMF for ZVI magnetization and a large reactor for removing contaminants by magnetized ZVI can be employed as a new method of ZVI-mediated remediation.

Simultaneous removal of arsenate and fluoride from water by AI-Fe （hydr）oxides

A1-Fe （hydr）oxides with different A1/Fe molar ratios （4：1, 1：1, 1：4, 0：1） were prepared using a co- precipitation method and were then employed for simultaneous removal of arsenate and fluoride. The 4A1 ： Fe was superior to other adsorbents for removal of arsenate and fluoride in the pH range of 5.0-9.0. The adsorption capacity of the A1-Fe （hydr）oxides for arsenate and fluoride at pH 6.50.3 increased with increasing A1 content in the adsorbents. The linear relationship between the amount of OH released from the adsorbent and the amount of arsenate or fluoride adsorbent by 4A1 ： Fe indicated that the adsorption of arsenate and fluoride by A1- Fe （hydr）oxides was realized primarily through quantita- tive ligand exchange. Moreover, there was a very good correlation between the surface hydroxyl group densities of A1-Fe （hydr）oxides and their adsorption capacities for arsenate or fluoride. The highest adsorption capacity for arsenate and fluoride by 4A1 ： Fe is mainly ascribed to its highest surface hydroxyl group density besides its largest pHpzc. The dosage of adsorbent necessary to remove arsenate and fluoride to meet the drinking water standard was mainly determined by the presence of fluoride since fluoride was generally present in groundwater at much higher concentration than arsenate.

Co-present Pb(Ⅱ)accelerates the oxidation of organic contaminants by permanganate:Role of Pb(Ⅲ)

The permanganate(Mn(VII))oxidation has emerged as a promising technology for the remediation and treatment of the groundwater and surface water contaminated with the organic compounds.Nonetheless,only a few studies have been conducted to explore the role of the heavy metals(especially the redox-active ones)during the Mn(VII)oxidation process.In this study,taking Pb(II)as an example,its influence on the Mn(VII)decontamination performance has been extensively investigated.It was found that,with the presence of Pb(II),Mn(VII)could degrade diclofenac(DCF),2,4-dichlorophenol,and aniline more effectively than without.For instance,over a wide pH range of 4.5–8.0,the dosing of 10μmol/L Pb(II)accelerated the DCF removal rate from 0.006–0.25 min–1 to 0.05–0.46 min–1 with a promotion factor of 1.9–9.4.Although the UV-vis spectroscopic and high resolution transmission electron microscopy analyses suggested that Mn(VII)could react with Pb(II)to produce Mn(IV)and Pb(IV)at pH 6.0–8.0,further experiments revealed that Pb(II)did not exert its enhancing effect through promoting the generation of MnO_(2),as the reactivity of MnO_(2)was poor under the employed pH range.At pH below 5.0,it was interesting to find that,a negligible amount of MnO_(2)was formed in the Mn(VII)/Pb(II)system in the absence of contaminants,while once MnO_(2)was generated in the presence of contaminants,it could catalyze the Pb(II)oxidation to Pb(IV)by Mn(VII).Collectively,by highlighting the conversion process of Pb(II)to Pb(IV)by either Mn(VII)or MnO_(2),the reactive Pb(III)intermediates were proposed to account for the Pb(II)enhancement effect.